package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.List;

/**
 * This {@link IndexDeletionPolicy} implementation that keeps only the most
 * recent commit and immediately removes all prior commits after a new commit is
 * done. This is the default deletion policy.
 */

public final class KeepOnlyLastCommitDeletionPolicy implements
		IndexDeletionPolicy {

	/**
	 * Deletes all commits except the most recent one.
	 */
	public void onInit(List commits) {
		// Note that commits.size() should normally be 1:
		onCommit(commits);
	}

	/**
	 * Deletes all commits except the most recent one.
	 */
	public void onCommit(List commits) {
		// Note that commits.size() should normally be 2 (if not
		// called by onInit above):
		int size = commits.size();
		for (int i = 0; i < size - 1; i++) {
			((IndexCommitPoint) commits.get(i)).delete();
		}
	}
}
